Methods and circuits for improved reliability of power devices operating under repetitive thermal stress

ABSTRACT

Thermo-migration induced stress in power devices can be mitigated by deactivating a subset of power device components (e.g., transistors, etc.) when the power device experiences a high stress condition. Deactivating the subset of power device components serves to bifurcate the active area of the power switching device into smaller active regions, which advantageously changes the temperature gradients in the active area/regions. In some embodiments, a control circuit dynamically deactivates different subsets of power device components to shift the thermo-migration induced stress points to different portions of the active region over the lifetime of the power switching device.

TECHNICAL FIELD

The present invention relates generally to power devices, and inparticular embodiments, to techniques and mechanisms for methods andcircuits for improved reliability of power devices operating underrepetitive thermal stress.

BACKGROUND

Power devices generally include semiconductor devices or integratedcircuits that are used as switches or rectifiers in power electronics,e.g., a switch-mode power supply, etc. Power devices may typicallyoperate in a “commutation mode” in which they are either in a conductingstage (e.g., switched-on) or non-conducting stage (e.g., switched-off).During the conducting stage, thermo-mechanical stress may causemetallization degradation/destruction in the active area of a powerdevice, which may lead to failure over time, e.g., shorts, etc. Morespecifically, high power transient events, like inductive clamping, maygenerate high transient local temperatures and high temperaturegradients, which may cause metal/thermo migration (thermal drivenmigration of the metals) in chip components (e.g., metal lines, etc.).Indeed, metal/thermo migration may exert non-uniform stresses duringeach high power cycle until the inter-metal dielectric cracks and/or thepower device fails.

One solution for reducing thermo-migration induced stress in powerdevices is to reduce the peak temperature during the high power pulseevents, which is generally achieved by increasing the size of the powerdevice's active area. However, increasing the size of the power devicemay be undesirable for applications requiring relatively small and/orcompact semiconductor packaging. Accordingly, alternative techniques forreducing thermo-migration induced stress in power devices are desired.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe methods and circuits for improved reliabilityof power devices operating under repetitive thermal stress.

In accordance with an embodiment, a method for regulating a power deviceis provided. In this example, the method includes sensing when a powerswitching device is experiencing a high stress condition. The powerswitching device comprises an input port, an output port, and powerdevice components coupled between the input port and the output port. Anelectrical current flows between the input port and the output port whenthe power switching device experiences the high stress condition. Themethod further includes activating a first subset of the power devicecomponents without activating a second subset of the power devicecomponents in response to the power switching device experiencing thehigh stress condition. The electrical current flows through the firstsubset of power device components without flowing through the secondsubset of power device components when the power switching deviceexperiences the high stress condition.

In accordance with another embodiment, another method for regulating apower device is provided. In this example, the method includes sensingwhen a power switching device is experiencing a high stress condition.The power switching device comprises an input port, an output port, andpower device components coupled between the input port and the outputport. An electrical current flows between the input port and the outputport when the power switching device experiences the high stresscondition. The method further includes dynamically deactivatingdifferent subsets of the power device components during differentperiods. At least some of the power device components remain activatedduring each of the periods. The electrical current flows throughactivated power device components without flowing through the subset ofpower device components that are deactivated during a given period whenthe power switching device experiences the high stress condition.

In accordance with yet another embodiment, a power switching device isprovided. In this example, the power switching device comprises an inputport adapted to be coupled to a load, an output port adapted to becoupled to a sink, and a plurality of power device components coupledbetween the input port and the output port. Electrical current flowsbetween the input port and the output port when the power switchingdevice experiences a high stress condition. A first subset of the powerdevice components are de-activated when the power switching deviceexperiences a high stress condition during a first period, and a secondsubset of the power device components remain activated when the powerswitching device experiences the high stress condition during the firstperiod. The electrical current flows through the second subset of powerdevice components without flowing through the first subset of powerdevice components when the power switching device experiences the highstress condition during the first period.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a circuit diagram of an embodiment power switchingdevice;

FIG. 2 illustrates a circuit diagram of another embodiment powerswitching device;

FIG. 3 illustrates a circuit diagram of an embodiment selection circuitfor selecting different subsets of transistors to deactivate duringdifferent periods of power device operation;

FIG. 4 illustrates a circuit diagram of another embodiment selectioncircuit that is configured to sense temperature, current, and voltage inthe active area of a power device to identify high stress events;

FIG. 5 illustrates a timing diagram for the embodiment selection circuitdepicted in FIG. 4;

FIG. 6 illustrates a diagram of an embodiment sensor array formonitoring stress in the active area of a power device;

FIG. 7 illustrates a diagram of an embodiment metal line sensor arrayfor monitoring stress in the active area of a power device;

FIG. 8 illustrates a diagram of an embodiment temperature sensor arrayfor monitoring stress in the active area of a power device;

FIG. 9 illustrates a graph of a temperature distribution in an activearea of a conventional power switching device during a high stressperiod;

FIG. 10 illustrates a graph of a temperature distribution in an activearea of an embodiment power switching device having a subset oftransistors deactivated during a high stress period;

FIG. 11 illustrates a graph of temperature distribution and a graph oftemperature profiles along four Y-axis in the active area of theconventional power switching device depicted in FIG. 9;

FIG. 12 illustrates a graph of temperature gradients magnitudedistribution and a graph of temperature gradients profiles along thefour Y-axis depicted in FIG. 11;

FIG. 13 illustrates a graph of temperature distribution and a graph oftemperature profiles along four Y-axis in the active area of theembodiment power switching device depicted in FIG. 10;

FIG. 14 illustrates a graph of temperature gradients magnitudedistribution and a graph of temperature gradients profiles along thefour Y-axis depicted in FIG. 13;

FIG. 15 illustrates a graph comparing probabilities of failure for powerdevices having different configurations;

FIG. 16 illustrates a diagram of an embodiment processing system.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of embodiments of this disclosure are discussed indetail below. It should be appreciated, however, that the conceptsdisclosed herein can be embodied in a wide variety of specific contexts,and that the specific embodiments discussed herein are merelyillustrative and do not serve to limit the scope of the claims. Further,it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of this disclosure as defined by the appended claims.

Aspects of this disclosure reduce thermo-migration induced stress inpower devices by deactivating a subset of power device components (e.g.,transistors, etc.) when the power device experiences a high stresscondition. Deactivating the subset of power device components serves tobifurcate the active area of the power switching device into smalleractive regions, which advantageously changes the temperature gradientsin the active area/regions, e.g., the axis running parallel to thecurrent flow in some implementations. In some embodiments, a controlcircuit dynamically deactivates different subsets of power devicecomponents to shift the thermo-migration induced stress points todifferent portions of the active region over the lifetime of the powerswitching device. Various techniques can be used to select which subsetsof power device components are deactivated during a given period ofoperation. For example, subsets of power device components can beselected randomly or according to a predefined pattern, e.g., a patterndeveloped during simulation and/or testing to extend the averagelifetime of a power switching architecture. Alternatively, the subsetsof power device components can be selected based on readings from stresssensors. The stress sensors may be any sensor whose readings can be usedto determine/predict which portions of the active area have experiencedstress, including temperature sensors and mechanical stress sensors.Notably, in some situations, manipulation of temperature gradients mayextend the lifetime of a power device even when the peak temperature isincreased. Similarly, deactivating a subset of power device componentsimprove the overall life expectancy of a power device even though thetemperature gradients are increased across some portions of the activearea. Advantageously, deactivating subsets of power device componentsdoes not significantly affect the on-state resistance of the powerdevice. These and other aspects are discussed in greater detail below.

Aspects of this disclosure can be embodied in power switching devicescoupled to inductive loads. FIG. 1 illustrates a circuit diagram of anembodiment power switching device 100 coupled to an inductive load (L).As shown, the power switching device 100 comprises a gate driver 105, aplurality of transistors 110, 120, 130, a plurality of switches 115,125, and 135, and a Zener diode 150. Notably, the switches 115, 125, 135are configured to selectively open connections that carry activationsignals to gates of the transistors 110, 120, 130 during high stressperiods, thereby preventing the activation signal from activating thetransistors 110, 120, 130 during a high stress event. In thisdisclosure, the term “high stress period” is used synonymously with theterms “high stress cycle” and “high stress instance.”

More specifically, the transistors 110, 120, 130 have a source-drainpath coupled in-between the input (IN) and output (OUT) of the powerswitching device 100, as well as gates coupled to the Zener diode 150via connections C1, C2, C3 and to the gate driver 105 via a connection(C4). When one or more of the transistors 110, 120, 130 are activatedvia an activation signal or a triggering signal, electrical current ofthe inductive load (L) flows between the input (IN) and output (OUT)ports of the power switching device 100.

Activation signals are communicated over the connections C1, C2, C3 whenthe Zener diode 150 enters an avalanche mode, as may occur when theinductive load (L) voltage exceeds a threshold (which is indicative ofthe power switching device 100 experiencing a high stress condition).Indeed, the Zener diode 150 becomes shorted upon entering the avalanchemode, which elicits the activation signal to flow through the Zenerdiode 150 and over the connections C1, C2, C3 to the gates of thetransistors 110, 120, 130. One or more of the connections C1, C2, C3 maybe opened (or broken) by the switches 115, 125, 135. The switches 115,125, 135 may be any component or feature configured to break or open theconnections C1, C2, C3 (respectively) in order to prevent activationsignals from reaching gates of the corresponding transistors 110, 120,130 when the power switching device 100 is experiencing a high stresscondition. In an embodiment, a subset of the switches 115, 125, 135 arepermanently opened during a manufacturing process of the power switchingdevice 100. In another embodiment, different subsets of the switches115, 125, 135 are dynamically opened during different cycles ofoperation to migrate the thermo-induced stress points to differentportions of the active area over the lifetime of the power switchingdevice 100.

In some embodiments, deactivation of one or more of the transistors 110,120, 130 during high stress periods does not completely disable thedeactivated transistor, as the deactivated transistor can neverthelessbe actuated via a triggering signal. More specifically, a gate driver105 is configured to actuate the power switching device 100 bycommunicating a triggering signal over the connection C4 to the gates ofthe transistors 110, 120, 130. As used herein, the term “activationsignal” refers to a signal that is generated/elicited when a powerdevice experiences a high stress condition, while the term “triggeringsignal” refers to a control signal that is generated to actuate thepower device irrespective of whether the power device is experiencing ahigh stress condition. Markedly, the connections C1, C2, and C3 areseparate and distinct from the connection C4, such that a triggeringsignal can be communicated over the connection C4 to the gates of thetransistors 110, 120, 130 irrespective of whether one or more of theconnections C1, C2, and C3 are open. For example, a triggering signalcan be communicated over the connection C4 to the gate of the transistor120 even when the connection C2 is open. The transistors 110, 120, 130may be protected from overvoltage by the Zener diode 150. Otherprotection functionalities may also be implemented, e.g., short-circuitprotection, over-temperature protection, etc. The transistors 110, 120,130 may be cells or groups of cells which are part of the active area ofthe power device 100.

Aspects of this disclosure can also be embodied in a switching devicecoupled to a capacitive load. FIG. 2 illustrates a circuit diagram of anembodiment power switching device 200 coupled to a capacitive load (C).As shown, the power switching device 200 comprises gate drivers 205,208, a plurality of transistors 210, 220, 230, a plurality of switches215, 225, 235, and a current sensor (CT). The gate driver 205 and thetransistors 210, 220, 230 may be configured similarly to correspondingcomponents of the power switching device 100. For example, the gatedriver 205 may provide a triggering signal to gates of the transistors210, 220, 230 via the connection C4 to actuate the power switchingdevice 200. Moreover, the transistors 210, 220, 230 may conduct currentflowing from the input (IN) and output (OUT) ports of the powerswitching device 200 when a triggering or activation signal is receivedat their gates.

The current sensor 290 may be configured to detect when the powerswitching device 200 is experiencing a high load condition, as well asto notify the gate driver 208 when the high load condition is detected,which may prompt the gate drive 208 to provide an activation signal tothe gates of the transistors 210, 220, 230 via the connections C1, C2,C3. The switches 215, 225, 235 may be configured similar to the switches115, 125, 135 in the power switching device 100. For example, theswitches 215, 225, 235 may be statically or dynamically configured tobreak/open the connections C1, C2, C3. While the power switching devices100, 200 are depicted as comprising transistors, thearchitectures/techniques described herein can be applied to powerdevices that include any type of power device component, e.g., diodes,thyristors, etc, because the method increases the lifetime of themetallization system (which is part of the power device component).Accordingly, aspects of this disclosure that are discussed in thecontext of “transistors” are applicable to any type of power devicecomponent, unless otherwise specified. The lifetime of a power device orsystem may be determined largely by its weakest point, and aspects ofthis disclosure can shift the stress points away from the weak points(or points that have received the most stress up to that stage) toincrease the lifetime.

In some embodiments, a control circuit dynamically deactivates differentsubsets of power device components to shift thermo-migration inducedstress points to different portions of the active region over thelifetime of the power switching device. In one example, a new subset ofpower device components are deactivated after a predefined number ofhigh stress instances. FIG. 3 illustrates an embodiment selectioncircuit 300 for selecting different subsets of transistors to deactivateduring different periods of operation. As shown, the embodimentselection circuit 300 includes a comparator 310 that detects when thepower switching device is experiencing a high stress condition, acounter 320 that tracks the number of instances in which the comparator310 detects the high stress condition, and a partition decoder 330 thatselects which subset of power device components are to be deactivatedduring the next operating period. In this example, the comparator 310detects a voltage rise when the clamping circuit (e.g., the Zener chain)is triggered, and sends a count signal to the counter 320. Afterreceiving a threshold number of count signals, the counter 320 promptsthe partition decoder 330 to select a new subset of power devicecomponents to deactivate during the next operating period.

The selection circuit 300 further includes an initial state generator325 that stores an initial state for the counter 320, as well as a statedecoder 340 and flash memory 350 that record the number of clampingevents that are triggered while the counter 320 is powered-on. The statedecoder 340 and flash memory 350 may be excluded in some embodiments, inwhich case the counter 320 may prompt the partition decoder 330 toselect a new subset of power device components to deactivate during eachconsecutive high stress period. The counter 320 can be powered off toreset the counter 320, which may cause the selection circuit 300 torevert back to an initial state during the next clamping event.

In some embodiments, the high stress condition may be detected usingtemperature and/or current sensors in the active area of a power device.FIG. 4 illustrates an embodiment selection circuit 400 that isconfigured to sense temperature/current to determine high stress eventsof a power device. The power device comprises an active area 401 and adriver 405 configured to actuate/activate power device components in theactive area 401. The power device components in the active area 401 maybe partitioned into groups of one or more power device components. Thegroups may be monitored by various sensors, including temperaturesensors and/or current sensors. As shown, the embodiment selectioncircuit 400 includes a high power detector 410 that detects instances ofhigh stress in the power device, a counter 420 that tracks the number ofhigh stress instances, an initial state generator 425 that stores aninitial state for the counter 420, and a partition decoder 430 thatselects subsets of power device components to be deactivated during thedifferent operating periods. Notably, the high power detector 410 maydetect high stress instances in a variety of ways. In one example, thehigh power detector 410 detects that a high stress instance has occurredwhen a temperature (or temperature differential) in the active areaexceeds a threshold. In another example, the high power detector 410detects that a high stress instance has occurred when a current flowingthrough the active area exceeds a threshold. In yet another example, thehigh power detector 410 detects that a high stress instance has occurredwhen a power level (e.g., ISout*Vout) in the active area exceeds athreshold.

FIG. 5 illustrates a timing diagram 500 for the embodiment selectioncircuit 400, which shows different ways of detecting high stressconditions. In one example, the high power detector 410 provides a countsignal (e.g., HP out) in response to an active area temperatureexceeding an upper threshold. The high power detector 410 continues toprovide the count signal until the active area temperature falls below alower threshold. In another example, the high power detector 410provides a count signal (e.g., HP out) in response to a power level inthe active area exceeding a threshold. The power level may be determinedusing the current (e.g., IS_(OUT)) and voltage (V_(OUT)) readings takenfrom the active area. The high power detector 410 continues to providethe count signal until the power level falls below the threshold

Various techniques can be used to select which subsets of powercomponents to deactivate during a given operating period. In oneembodiment, the subsets of power device components are selectedrandomly. In another embodiment, the subsets of power device componentsare selected based on a predefined pattern. The predefined pattern mayhave been shown to provide some desirable performance characteristic(e.g., extend the average lifetime while still maintaining certainperformance levels) during simulation and/or testing.

As yet another alternative, the subsets of power device components canbe selected in accordance with readings from stress sensors, such astemperature sensors, mechanical stress sensors, and/or other sensorswhose readings can be used to determine/predict whichportions/components have experienced stress. This may allow the stresspoints to be shifted based on the actual (or projected) stress levelsexperienced by the device. FIG. 6 illustrates a sensor array 600 adaptedto monitor the active area of a power device. As shown, differentsensors in the sensor array 600 monitor different portions of the activeregions. The sensor array 600 may include temperature sensors,mechanical stress sensors, or other sensors adapted to monitor stress.The sensor array 600 may provide real-time stress detection informationfor use in selecting subsets of transistors over the lifetime of a powerswitching device.

One type of mechanical stress sensor is a metal line stress sensor. FIG.7 illustrates a metal line stress sensor array 700 for monitoring stressin active area of a power device. The metal lines can be embedded in themetallization of power device components, and may be adapted to sensethe stress distribution based on the variation in resistance of eachmetal line. In an embodiment, the metal line stress sensor array 700measures stress indirectly by monitoring a resistance/voltage change dueto mass migration and/or piezoelectric effects. The sensors in the metalstress sensor array 700 can be individual parts within thesemiconductor-metal-dielectric system, or a combination of parts withinthe semiconductor-metal-dielectric system. Temperature sensors may alsobe used to monitor stress. FIG. 8 illustrates a temperature sensor array800 for monitoring stress in active area of a power device. Thetemperature sensor array 800 may be adapted to create a temperature mapof the active region, which may be used to establish a directcorrelation between temperature distribution and mechanical stress.

Aspects of this disclosure substantially increase the lifetime of powerdevices by reducing and redistributing thermo-mechanical stress. FIG. 9illustrates a graph of a temperature distribution in an active area 900of a conventional power switching device having all transistorsactivated. FIG. 10 illustrates a graph of a temperature distribution inan active area 1000 in an embodiment power switching device having asubset of transistors deactivated. As shown, the deactivated transistorsare located in the center of the active area 1000, and serve tobifurcate the active area into two active regions positioned on oppositesides of the deactivated transistors. Notably, the two active regionshave a reduced size, which advantageously changes the temperaturegradient in the active regions. It should be appreciated that FIG. 10illustrates merely one of many configurations in which deactivatedtransistors can bifurcate/subdivide an active area into two or moreactive regions to achieve changed temperature gradients. In otherconfigurations, different subsets of transistors may be deactivated tosubdivide the active area into different sub-regions, e.g., differentnumbers of sub-regions, non-uniform sub-regions having different widths,etc.

FIG. 11 illustrates temperature profiles along four Y-axis in the activearea 900 of the conventional power switching device, and FIG. 12illustrates temperature gradients along those four Y-axis. FIG. 13illustrates temperature distributions along four Y-axis profiles in theactive area 1000 of the embodiment power switching device, while FIG. 14illustrates temperature gradients along those four Y-axis profiles. Asshown, the active area 1000 of the embodiment power switching deviceachieves different temperature gradients than the active area 900 of theconventional power switching device, which is beneficial from thereliability point of view.

This modification in temperature gradients increases the averagelifetime of the embodiment power switching device. FIG. 15 illustrates agraph comparing probabilities of failure of power devices having threedifferent configurations. First configuration: a conventional powerdevice which has all transistor subsets turned on during high stressperiods. Second configuration: a power device which has a transistorsubset deactivated for all high stress periods. Third configuration: apower device that alternates between having a subset of transistorsdeactivated and having all transistors activated during high stressperiods. As shown, both of the embodiment power devices have longerlifetimes than the conventional power device. As shown, both of theembodiment power devices have lower probabilities of failure than theconventional power devices after a comparable number of stress cycles.Note that devices from third configuration do not have lifetimes twotimes larger than devices from the first configuration, as was expected.Actually, these devices survive longer because stress relaxation occursdue to direction changes of temperature gradients during the period whenthe device operates with one subset deactivated.

High local temperatures and non-uniform temperature distribution(thermal gradients) induce mechanical stress in transistormetallization. Embodiment techniques provided herein control thetemperature gradients and peak temperature by modulating the powerdistribution in the device. Modulating the power distribution does notreduce the total power dissipated by the device. The average temperatureon the surface of the device (e.g., the temperature integrated over thesurface) is higher in the conventional case of FIG. 9 than in theembodiment device of FIG. 10 and the peak temperatures are approximatelythe same for the devices tested, therefore the temperature gradientsdiffer between devices. Drain current modulation may be used to modulatethe power device for power distribution control. Drain currentmodulation may be adjusted from the gate and bulk terminals of eachcell/group of cells. Drain-source voltage distribution can also beadjusted from source, drain potentials.

In some embodiments, power distribution is adjusted over the lifetime ofthe power device according to data measured by thermo-mechanical stresssensors embedded in the power device. In other embodiments, powerdistribution is adjusted over the lifetime of the power device accordingto a predefined pattern, which may be a pattern that is derived fromsimulations and/or testing. An appropriate detection-biasing scheme canbe used to control mechanical stress increment per power cycle, as wellas to control the rate of accumulation of the peak mechanical stress. Tobetter illustrate this consider that a transistor undergoesthermo-mechanical stress as result of high temperature/power cycling.During its lifetime, peak mechanical stress builds somewhere in themetallization in a region. From sensor or simulation data, a subset ofcells of power device components is adjusted in a manner that shifts thepeak stress away from that region after a period of time, such that thepeak mechanical stress is exerted on a different region. The processrepeats and the stress is distributed uniformly in the metallization.

Embodiments of this disclosure reduce/mitigate thermal-induced stresswithout significantly increasing the size of the active area and/or chiparea. Embodiments of this disclosure achieve a variation in thetemperature distribution in the power device over the course of itslifetime by deactivating different subsets of transistors duringdifferent periods. This may extend the lifetime of the power device byachieving a more uniform mechanical stress distribution. Temperaturedistribution control is achieved by power distribution modulation. Thepower distribution is, in turn, controlled by conveniently biasinggroups of cells (subsets) within the transistor. By applying acorresponding bias to the terminals of each cell or group of cells, thecurrent-density and/or drain-source voltage can be locally adjusted inreal-time to achieve a power density distribution that leads to moreevenly distributed mechanical stress in the metallization of the powerdevice. Thermo-mechanical stress sensors can be used to obtaininformation on the mechanical stress evolving in the metallization.

Embodiments of this disclosure can be applied to any type of powerdevice, including power devices incorporating double-diffusedmetal-oxide-semiconductor (DMOS) transistors, bipolar junctiontransistors (BJT), insulated-gate bipolar transistors (IGBTs). Indeed,embodiments of this disclosure can be applied to any device acting as aheating element or heat source, as it enhances the lifetime of itsmetallization system.

Over its lifetime, a transistor is subject to multiple high power pulseevents which cause heating of the device and high local temperaturetransients. In addition, the non-uniform heating of the device generateshigh temperature gradients. High temperatures and high temperaturegradients are present both in the power device (Silicon surface) and inits metallization system (metal films and dielectric which separates themetals). These two conditions cause different expansions in the Silicon,metal, and dielectric, which generates mechanical stresses at thecorresponding junctions. The stress accumulates with each high powerpulse event until the system ultimately fails.

Practically speaking, most high power pulses are generated when theswitch operates with an inductive load or when the switch operates witha capacitive load. When the switch operates with an inductive load, atturn-off, a high power pulse is dissipated in the device (inductiveclamping event). On the other hand, when the switch operates with acapacitive load, at turn-on, a high power pulse is dissipated in thedevice. Embodiments of this disclosure provide techniques for reducingthe resulting thermo-mechanical stress during those switching events.

FIG. 16 illustrates a block diagram of a processing system 1600 that maybe used for implementing the devices and methods disclosed herein. Theprocessing system 1600 may include a processor 1604, a memory 1606, anda plurality of interfaces 1610-1614, which may (or may not) be arrangedas shown in FIG. 16. The processor 1604 may be any component capable ofperforming computations and/or other processing related tasks, and thememory 1606 may be any component capable of storing programming and/orinstructions for the processor 1604. The interfaces 1610-1614 may be anycomponent or collection of components that allows the processing system1600 to communicate with other systems and/or devices. The interfaces1610-1614 may include serial interfaces (e.g., a Serial PeripheralInterface (SPI), Universal Serial Bus (USB), etc.), parallel interfaces,or combinations thereof.

Although the description has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade without departing from the spirit and scope of this disclosure asdefined by the appended claims. Moreover, the scope of the disclosure isnot intended to be limited to the particular embodiments describedherein, as one of ordinary skill in the art will readily appreciate fromthis disclosure that processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped, may perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein. Accordingly, the appended claims are intended to include withintheir scope such processes, machines, manufacture, compositions ofmatter, means, methods, or steps.

What is claimed:
 1. A method comprising: sensing when an active regionin an active area of a power switching device is experiencing at least athreshold amount of thermo-mechanical stress, wherein the powerswitching device comprises an input port, an output port, and a set ofpower device components coupled between the input port and the outputport, wherein the active region of the power switching device includesactivated power device components in the set of power device components,and wherein electrical current flows from the input port over the activeregion to the output port when the power switching device is in aconducting stage; and activating a first subset of the power devicecomponents without activating a second subset of the power devicecomponents to dynamically bifurcate a shape of the active region into aplurality of active sub-regions in response to sensing that the activeregion in the active area of the power switching device is experiencingat least the threshold amount of thermo-mechanical stress, wherein theelectrical current flows through the first subset of the power devicecomponents without flowing through the second subset of the power devicecomponents when the power switching device is in the conducting stage,wherein dynamically bifurcating the shape of the active region reduces atemperature gradient of the active region.
 2. The method of claim 1,wherein activating the first subset of the power device componentswithout activating the second subset of the power device componentschanges the temperature gradient across the active area of the powerswitching device.
 3. The method of claim 1, wherein the power devicecomponents comprise transistors, the first subset of the power devicecomponents corresponding to a first subset of the transistors, and thesecond subset of the power device components corresponding to a secondsubset of the transistors, and wherein the power switching devicefurther comprises a first subset of connections adapted to carryactivation signals to gates of the first subset of the transistors, anda second subset of connections adapted to carry activation signals togates of the second subset of the transistors.
 4. The method of claim 3,wherein the second subset of connections are opened, while the firstsubset of connections are closed, and wherein the second subset ofconnections being opened prevents the activation signals from reachingthe gates of the second subset of the transistors when the powerswitching device is in the conducting stage.
 5. The method of claim 4,wherein the power switching device further comprises a third subset ofconnections adapted to carry triggering signals from a gate driver tothe gates of the transistors when the power switching device is actuatedby the gate driver, and wherein the third subset of connections isindependent from the second subset of connections such that thetriggering signals are provided to the gates of the second subset of thetransistors during actuation of the power switching device irrespectiveof the second subset of connections being opened.
 6. The method of claim5, wherein the second subset of connections are permanently openedduring a manufacturing process of the power switching device.
 7. Themethod of claim 1, wherein sensing when the active region in the activearea of the power switching device is experiencing at least thethreshold amount of thermo-mechanical stress comprises using an array ofthermo-mechanical stress sensors disposed in the active area.
 8. Themethod of claim 7, wherein the array of thermo-mechanical stress sensorscomprises a metal line stress array sensor.
 9. The method of claim 7,wherein the array of thermo-mechanical stress sensors comprises aplurality of temperature sensors disposed within the active area. 10.The method of claim 1, wherein sensing comprises using a temperaturesensor.
 11. The method of claim 1, wherein sensing comprises using amechanical stress sensor.
 12. A method comprising: sensing when anactive area in an active region of a power switching device experiencesat least a threshold amount of thermo-mechanical stress, wherein thepower switching device comprises an input port, an output port, andpower device components coupled between the input port and the outputport, and wherein electrical current flows between the input port andthe output port when the power switching device is in a conductingstage; and dynamically deactivating different subsets of the powerdevice components during different periods to dynamically bifurcate ashape of the active region of the power switching device into aplurality of active sub-regions, wherein at least one of the powerdevice components remains activated during each of the differentperiods, and bifurcating the shape of the active region reduces atemperature gradient of the active region, and wherein the electricalcurrent flows through activated power device components without flowingthrough the different subsets of the power device components that aredeactivated during a given period when the power switching device is inthe conducting stage.
 13. The method of claim 12, wherein dynamicallydeactivating the different subsets of the power device components duringthe different periods comprises: selectively deactivating the differentsubsets of the power device components in accordance with a randomselection criteria.
 14. The method of claim 12, wherein dynamicallydeactivating the different subsets of the power device components duringthe different periods comprises: selectively deactivating the differentsubsets of the power device components in accordance with a predefinedpattern.
 15. The method of claim 12, wherein dynamically deactivatingthe different subsets of the power device components during thedifferent periods comprises: selectively deactivating the differentsubsets of the power device components in accordance with readings fromstress sensors configured to measure a thermo-mechanical stress of theactive area.
 16. The method of claim 15, wherein the stress sensors aretemperature sensors.
 17. The method of claim 15, wherein the stresssensors are mechanical stress sensors.
 18. The method of claim 15,wherein the power device components comprise transistors, wherein thepower switching device further comprises a first subset of connectionsadapted to carry activation signals to gates of a first subset of thetransistors, and a second subset of connections adapted to carryactivation signals to gates of a second subset of the transistors, andwherein dynamically deactivating the different subsets of the powerdevice components during the different periods comprises: opening thefirst subset of connections during a first period, wherein opening thefirst subset of connections prevents the activation signals fromactivating the first subset of the transistors during the first period;and opening the second subset of connections during a second period,wherein opening the second subset of connections prevents the activationsignals from activating the second subset of the transistors during thesecond period.
 19. The method of claim 18, further comprising: sendingtriggering signals over a third subset of connections during the firstperiod, the third subset of connections extending from a gate driver togates of the transistors, wherein the third subset of connections areindependent from the first subset of connections such that thetriggering signals activate the first subset of the transistors when thepower switching device is actuated during the first period irrespectiveof the second subset of connections being opened.
 20. A power switchingdevice comprising: an input port adapted to be coupled to a load; anoutput port adapted to be coupled to a sink, wherein electrical currentflows between the input port and the output port when the powerswitching device is in a conducting stage; a thermo-mechanical stresssensor configured to measure a thermo-mechanical stress of an activeregion of the power switching device; and a plurality of power devicecomponents coupled between the input port and the output port, wherein afirst subset of the power device components are de-activated when thethermo-mechanical stress sensor indicates that the active region of thepower switching device experiences at least a threshold amount ofthermo-mechanical stress during a first period to dynamically bifurcatea shape of the active region of the power switching device into aplurality of active sub-regions, wherein dynamically bifurcating theshape of the active region reduces a temperature gradient of the activeregion, and a second subset of the power device components remainactivated when the thermo-mechanical stress sensor indicates that theactive region of the power switching device experiences at least thethreshold amount of thermo-mechanical stress during the first period,and wherein the electrical current flows through the second subset ofthe power device components without flowing through the first subset ofthe power device components when the thermo-mechanical stress sensorindicates that the active region of the power switching deviceexperiences at least the threshold amount of thermo-mechanical stressduring the first period.
 21. The power switching device of claim 20,wherein the power device components comprise transistors havingdrain-source paths coupled between the input port and the output port,the first subset of the power device components corresponding to a firstsubset of the transistors, and the second subset of the power devicecomponents corresponding to a second subset of the transistors.
 22. Thepower switching device of claim 21, further comprising: a first subsetof connections configured to carry first activation signals to gates ofthe first subset of the transistors; a second subset of connectionsconfigured to carry second activation signals to gates of the secondsubset of the transistors; and a controller configured to open the firstsubset of connections during the first period without opening the secondsubset of connections when the active region of the power switchingdevice experiences at least the threshold amount of thermo-mechanicalstress during the first period.
 23. The power switching device of claim22, further comprising: a gate driver adapted to provide triggeringsignals when the power switching device is actuated; and a third subsetof connections configured to carry the triggering signals to gates ofthe transistors when the power switching device is actuated, wherein thethird subset of connections are independent from the first subset ofconnections such that the triggering signals activate the first subsetof the transistors when the power switching device is actuated duringthe first period irrespective of the first subset of connections beingopen.
 24. The power switching device of claim 21, wherein the powerswitching device further comprises: connections adapted to carryactivation signals to gates of the transistors; and a control circuitconfigured to dynamically open different subsets of the connectionsduring different periods to prevent the activation signals fromactivating a corresponding subset of the transistors when the activeregion of the power switching device experiences at least the thresholdamount of thermo-mechanical stress during a corresponding period. 25.The power switching device of claim 24, wherein the control circuit isadapted to selectively deactivate the different subsets of thetransistors during the different periods in accordance with a randomselection criteria.
 26. The power switching device of claim 24, whereinthe control circuit is adapted to selectively deactivate the differentsubsets of the transistors during the different periods in accordancewith a predefined pattern.
 27. The power switching device of claim 24,wherein the control circuit is adapted to selectively deactivate thedifferent subsets of the transistors during the different periods inaccordance with readings from the thermo-mechanical stress sensor. 28.The power switching device of claim 27, wherein the thermo-mechanicalstress sensor comprises temperature sensors.
 29. The power switchingdevice of claim 28, wherein the temperature sensors comprise a pluralityof temperature sensors disposed in the active region.
 30. The powerswitching device of claim 27, wherein the thermo-mechanical stresssensor comprises mechanical stress sensors.
 31. The power switchingdevice of claim 30, wherein the mechanical stress sensors comprise ametal line stress array sensor.
 32. The power switching device of claim21, wherein the input port is adapted to be coupled to an inductiveload, and wherein the power switching device further comprises: a chainof diodes, including at least a Zener diode, coupled between the inputport and gates of the transistors, the chain of diodes adapted to enteran avalanche mode when a voltage across at least one of the power devicecomponents exceeds a threshold; and connections extending between thechain of diodes and the gates of the transistors, the connectionsconfigured to carry activation signals to the gates of the transistorswhen the chain of diodes enter the avalanche mode, wherein a firstsubset of the connections extend between the chain of diodes and thegates of the second subset of the transistors, the first subset of theconnections being open during the first period, and wherein a secondsubset of the connections extend between the chain of diodes and thegates of the second subset of the transistors, the second subset of theconnections being closed during the first period.
 33. The powerswitching device of claim 32, wherein the second subset of theconnections are permanently open.
 34. The power switching device ofclaim 32, wherein at least some connections in the first subset of theconnections are closed during a second period.
 35. The power switchingdevice of claim 21, wherein the input port is adapted to be coupled to acapacitive load, and wherein the power switching device furthercomprises: a gate driver configured to actuate the power switchingdevice by providing a triggering signal to gates of the transistors; afirst subset of connections extending between the gate driver and thegates of the first subset of the transistors, the first subset ofconnections being open during the first period; and a second subset ofconnections extending between the gate driver and the gates of thesecond subset of the transistors, the second subset of connections beingclosed during the first period.
 36. The power switching device of claim35, wherein the second subset of connections are permanently open. 37.The power switching device of claim 35, wherein at least someconnections in the first subset of connections are closed during asecond period.